There has been a widespread shift from the historic telecommunications business model which fostered low unit volume, relatively high price proprietary system architectures to standards-based solutions built using commercial off-the-shelf (COTS) technology. One of the business drivers for this shift is the need for flexibility to respond to a rapidly changing network infrastructure and the need to keep operating and capital expenditures low. Catalyzing this shift are standards based technologies that adhere to specifications defined by industry sponsored standards making bodies. For example, the Advanced Telecom Computing Architecture (or AdvancedTCA™ hereinafter “ATCA”) based platform can be used by both, suppliers and end-users to construct ATCA standard-compliant solutions.
The ATCA specification is a series of industry standards that define scalable, standardized platform architecture to extend COTS to a broad spectrum of products from component vendors. ATCA compliant components and systems embody interoperable ATCA technology such as physical format, system management and software designed to deliver cost effective, reduced time-to-market, off-the-shelf solutions that can be incorporated into products ranging from high-availability, carrier-grade telecom, storage, and computing applications. ATCA is sponsored by the PCI (Personal Computer Interconnect)—Industrial Computer Manufacturers Group (PICMG®), a major industry standards body.
The ATCA Base Specification, PIGMG 3.0 Revision 1.0, ratified in Dec. 30, 2002 (hereinafter “the ATCA specification”), defines an open electromechanical architecture of a modular platform that may be constructed from commercial off-the-shelf components. The electromechanical architecture encompasses the rack and shelf (chassis) mechanical form factors, power parameters, cooling characteristics, core backplane fabric interconnects and system management architecture to enable the construction of a modular platform that is capable of receiving a multiplicity of ATCA compliant modular plug-in circuit boards (ATCA carrier cards). The ATCA compliant modular plug-in circuit boards feature an open electromechanical architecture also defined by the ATCA specification. The ATCA base specification together with other associated specifications define multiple fabric connections and support multiple protocols for control and data plane communications including Ethernet, Fibre Channel, InfiniBand, StarFabric, PCI Express, and RapidIO®.
The PICMG® Advanced Mezzanine Card (AMC) base specification, PIGMG AMC.0, Revision 1.0, published Jan. 3, 2005 (hereinafter referred to as the AMC.0 specification, the entire contents of which are incorporated herein by reference) adds versatility to the modularity provided by the ATCA specification. The AMC specification defines the base-level mechanical, management, power, thermal, interconnect (including I/O) and system management requirements for hot-swappable, field-replaceable, add-on mezzanine cards (or modules) which may be hosted by an ATCA or a proprietary carrier board. Each AMC Module is received into an AMC Connector, seated parallel to the host carrier card and configured for high-speed, packet-based serial communications between the AMC card and the carrier board.
There are six different form factors defined in the AMC specification which include two AMC module widths (W): the single width module (73.5 mm) and a double width module (148.5 mm); three heights (H) or thicknesses: compact (13.8 mm), mid-sized (18.96 mm) and full-sized (28.95 mm); and a single depth (D) (181.5 mm). The height (H) is measured in a direction normal to the major plane of the AMC card. The width (W) and height (H) dimensions lie along mutually perpendicular directions in a plane that is normal to the direction along which the depth (D) is measured. When the AMC module is mounted vertically, the width dimension is aligned vertically and the height or thickness dimension is aligned horizontally. The reverse is the case when the AMC module is mounted horizontally. Additionally, the AMC specification refers to three types of carrier board configurations—conventional, cutaway and hybrid.
The availability of AMC cards having a wide variety of form factors allows the cards to accommodate a rich mix of circuit elements and circuit topologies to support many different application architectures that can address the needs of diverse segments of the computer and telecommunications marketplace. The AMC architecture supports a number of transfer protocols with varying band widths as described in the subsidiary PICMG standard AMC3.0 for example. AMC cards extend the functionality of the ATCA carrier boards and permit multiple vendors to build technology solutions for transmission and switching equipment and allow these technology solutions to be used in multiple applications and in multiple vendor product lines. The ATCA standardization approach in general improves product reliability (allowing for industry standard hot swappable hardware and software, including power supplies and fans) and drives down prices-due in large part to greater economies of scale in manufacturing and less time spent on details standardized by ATCA (e.g., power, cooling, mechanical spacing and connectors issues).
Technology implementations based on the ATCA specification represent “big iron” solutions that are suited to telephone company central offices with high density needs: i.e., switching systems and transmission cross connects. These chasses are too massive for remote/enterprise applications. Likewise, ATCA blades feature a form factor that makes them unsuitable for edge applications such as cellular base stations, wire-line fiber pedestals, workgroup routers, modular servers, SAN storage boxes, network hubs (Wi-Fi/Wi-MAX), military, aeronautical, and medical applications. In response, the members of PICMG have recently ratified the MicroTCA specification (MicroTCA.0 R1.0, Jul. 6, 2006) (hereinafter “the MicroTCA specification”) which represents a culmination of effort that resulted in several earlier draft specifications such as, for instance, PICMG® MicroTCA.0 Draft 0.32, Apr. 15, 2005 et seq. The following discussion presents certain details regarding the structural and operational aspects of MicroTCA-standards based systems that are described in the publicly available short form specification derived from the PICMG® MTCA.0 Micro Telecommunications Computing Architecture (MicroTCA.0) specification. (MicroTCA and the μTCA are trademarks of PICMG. AdvancedTCA and AdvancedMC are registered trademarks of PICMG).
The MicroTCA specification utilizes the PICMG AMC form-factor and management infrastructure for mezzanine blades as set forth in the ATCA specification to define the standardized elements needed to implement a MicroTCA Shelf (or “Shelf” which is also known as the chassis), including power modules, cooling elements, connectors, interconnects, backplane, MicroTCA Carrier Hub (MCH) and the subrack. The Shelf may be configured to realize diverse small foot-print, low-cost, flexible, and scalable platforms comprised entirely of AMC modules and interoperable components and systems. The thrust of MicroTCA is the reuse of technology defined by the AMC standard so that an AMC card (or module) can be used with either an ATCA carrier board or a “MicroTCA Carrier”.
The “MicroTCA Carrier” as the term is used in MicroTCA, refers to the elements of a MicroTCA Shelf defined in AMC.0 including, among others, cooling and power delivery elements, a backplane with clock, fabric, power and management interconnects, and centralized hardware management that collectively emulate the requirements of the ATCA carrier board and can nominally support up to 12 AMC modules. Each AMC module plugs directly into the MicroTCA backplane instead of an ATCA based carrier board. A MicroTCA system consists of at least one AMC card. Additionally, a MicroTCA system also consists of at least one MicroTCA-specific module not defined by the AMC.0 specification. For example, a MicroTCA system consists of at least one AMC card and at least one MicroTCA-specific AMC-sized card called a MicroTCA Carrier Hub (MCH). The MCH combines the control and management infrastructure and the interconnect fabric resources needed to support up to 12 AMC modules. The MCH also contains IPMI software for managing key chassis functions, as well as clocking AMC daughter cards for different applications. Another MicroTCA-specific component is the power module, which fits in the same form factor as an AMC card. Thus configured, the MicroTCA form factor targets communications equipment ranging from pole mounted devices to core routers and IP-gateways, radio base stations and switching centers.
The outer dimensions of a MicroTCA system are defined by the Shelf which is rack-mountable (or frame-mountable). The Shelf is the basic autonomous unit of a MicroTCA system. The rack-mountable Shelf may be divided by rack-mounted Cubes, free-standing Cubes or Pico subassemblies (alternatively enclosures) to be populated with AdvancedMC modules. A MicroTCA specification compliant Shelf is either the 19 in. Shelf as defined in IEC 60297 or the Metric Shelf as defined in IEC 60917. Height dimensions of Shelves are generally designed using increments of 1 U/SU to follow common equipment practice where 1 U=44.45 mm or 1.75 in.
By definition, the Shelf contains at least a portion of a MicroTCA “Subrack.” A Subrack is a mechanical assembly that provides the structural support for Shelf elements such as the AMCs, the MicroTCA Carrier elements and the backplane. A Shelf element may be a board typically comprising of components mounted on a printed circuit, an electromechanical assembly such as a fan module or a mechanical component such as a filter. The Subrack serves to receive, locate and enclose the electronic components in relative alignment to each other within the Shelf or chassis. The Subrack is also equipped with the mounting holes, card guides, cable guides, mounting brackets, EMC/ESD control structures, handle interface, face plate mounting hardware, air-flow guiding means and associated features. The standard orientation of the Subrack is vertical. When oriented in the horizontal direction, the vertical dimensions are followed. In the vertical direction, Subracks are divided into subsections of Tiers. The minimum requirement is one Tier; the maximum may be 4 Tiers. In the horizontal direction, Subracks are divided into subsections of slots where a slot is defined as a union of a connector and a card guide and defines the position of one AMC, MCH, or Power Module (PM). A MicroTCA Subrack can contain multiple Slots. Full-Height Modules, Mid-Size Modules and Half-Height Modules may be mixed and arranged in any order, horizontally across the MicroTCA Subrack.
A MicroTCA shelf can be configured to accommodate a large number of AMCs combined in multiple Tiers to achieve a high system density. The basic MicroTCA shelf equipped with 12 AMC modules can provide an overall chassis capability of (12.5 Gbps/per AMC.0 card×12 AMC.0 cards) 150 Gbps. The physical dimensions of the standard Shelf make it too large for certain applications such as, for instance, game boxes, personal computers, single board computers, SATA/SAS storage modules, and WiMAX modules that are designed for operation on mobile platforms. Furthermore, many applications may not need the capacity that the full complement of 12 AMC.0 cards can provide. To accommodate such situations, the MicroTCA standard provides for special MicroTCA Shelves such as the MicroTCA Cube Shelf and MicroTCA Pico Shelf that can be configured for space-constrained applications while providing the desired level of functionality by leveraging the compact size of the AMCs. Each of these mechanical infrastructures can accommodate different complements of AMCs depending upon the size of the AMC, MCH capacity, enclosure width, and enclosure height. Certain architectures, such as the Pico Shelf architecture, are not required to contain a standalone MCH or PM. Instead, connections can be made directly between the various AMC modules using the backplane or between the AMC modules and elements on the backplane.
The MicroTCA specification leaves many design details of the Subrack undefined. The Subrack essentially defines only the AMC.0, MCH, and Power Module interfaces and the dimensions which govern the interface of AdvancedMC Modules to the Subrack and Backplane. All other Shelf architecture (including, the Cube Shelf and the Pico Shelf) dimensions remain undefined. Likewise, Subrack materials and design details are left undefined. Similarly, a MicroTCA shelf design (including the Pico Shelf) may have to comply with thermal, acoustic, shock and vibration related functional specifications imposed by the MicroTCA standard. The specification does not, however, provide a reference mechanical design capable of meeting these requirements. It is thus possible to design a large number of systems that conform to the specification. For example, the MicroTCA standard supports six form-factors for the AMC cards. The largest form factor is the Full-Height, Double-Width (Double Full-Size) AMC which occupies a mechanical volume of 150 (W)×187.3 (D)×30.48 mm (H). However, this volume can be subdivided into some number of smaller AMCs that fit into an enclosure with a smaller foot-print.
It is also possible to design systems that conform to the specification but include non-compliant components and subsystems where the specification is silent thereby considerably extending the range of technology solutions covered by the scope of the specification. The MicroTCA specification prescribes that the MCH, PM, CU and AMCs be Field Replaceable Units (FRUs). As noted in the MicroTCA specification, a particularly challenging aspect of the mechanical design is an option to permit in-field re-configuration of numerous and various types of AMCs, used in multiple positions in a MicroTCA Shelf. (See, section 1.2.4.5 of the MicroTCA Specification).
It would be advantageous to provide a modular, scalable electronic enclosure that conforms to the MicroTCA specification, accommodates non-compliant architecture where not prohibited by the MicroTCA specification, permits in-filed re-configuration of the AMC modules in multiple positions in the MicroTCA Shelf, facilitates in-field reconfiguration of the shelf geometry without the need to relax the geometrical tolerances required by the MicroTCA specification and is sufficiently versatile to accommodate the requirements of an evolving specification.